1. 1 Timing of the calorimeter monitoring signals 1.Introduction 2.LED trigger signal timing * propagation delay of the broadcast calibration command * calibration signal time-alignment with CLK 3. Updated specification of the 64 – channel LED Trigger Signal Board (LEDTSB) * an updated block diagram * 64 output channels divided on the four 16 channels groups with the programmable individual coarse delay up to 15 clock cycles. 4. Conclusion CALO meeting 22.04.04 Anatoli Konoplyannikov

2. 2 The estimation of the propagation delay of the LED monitoring signals for the calorimeter sub-detectors is very important for a correct synchronization time adjustment with the data Read Out. The main timing requirements to the L0 front-end electronics is formalized in LHCb technical notes. The default calibration signal type (type = 0) is made with a fixed timing of 16 + 160 clock cycles before the related trigger, which must then be time aligned by programmable delays in the front-ends. The additional 16 clock cycle spacing between the calibration signal and its trigger has been added to allow additional delays of the calibration signal in the front-end. Timing of the calorimeter monitoring signals Calibration pulse injection command timing (note LHCb 2001-014)

3. 3 CALO meeting 22.04.04 Anatoli Konoplyannikov Propagation delay of the broadcast calibration command The source of the calibration signal is the TTCrx broadcast command, generated by Read Out Supervisor. The format of this command is shown in Table 1. LHCb commandBit 7Bit6Bit5Bit4Bit3Bit2Bit1Bit0 CMD1 0001 Calibration pulse type: (calibration)0: Default 1 - 3: reserved The bits of the broadcast command is time-alignment with Clock40Des1 into the TTCrx chip. Then this command is distributed by LHCb TTC system to each detector and propagated throughout the detector specific chains. Timing of the calorimeter monitoring signals The L0 latency is 4  s and defined as the maximum delay from the actual bunch crossings to the L0 trigger decision arrives to the output of the L0 pipeline buffer in any sub-detector. For the calorimeter calibration signal timing it means that the total propagation delay from the TTCrx calibration command of the CROC board to the LED light pulse must be 16 clock cycles.

4. 4 CALO meeting 22.04.04 Anatoli Konoplyannikov In the calorimeter electronics this command is distributed by a CROC card to each slot of FE crate. There is no any delay time compensation of the bus length difference for different slots of the FE crate. The time spread of the broadcast command on the FE backplane could be up to 3 ns. Due to the reason mentioned above, an additional time-alignment with 40 MHz clock is needed and implemented in LED trigger signal board (LEDTSB). LEDTSB distributes the LED trigger pulses to LED drivers by a twisted pair cable with a different for each sub-detector length. Then a light pulse from LED comes to PMT through the optic fiber and from PMT the signal comes to FEB. The estimation of the calibration signal delay for all sequential chains will be shown later. In ECAL and HCAL case the LED intensity is monitoring by PIN diode. It is important to take into account that signal response from PTM and PIN diode comes in the different time, due to the optic paths from LED to PMT and from LED to PIN diode are different. The sketch of the monitoring signal chain for ECAL and HCAL sub-detectors is shown on figure and the monitoring signal delay time estimation presented in Table 2. Timing of the calorimeter monitoring signals

5. 5 CALO meeting 22.04.04 Anatoli Konoplyannikov Sketch of the ECAL and HCAL LED monitoring signal chain. LED monitoring signal chain elements: 1.Back plane of the FE crate. 2.LED triggering pulse distribution cable. 3.Light distribution optic fiber. 4.PMT signal transmission cable. 5.LED to PIN light fiber. 6.PIN signal transmission cable. Timing of the calorimeter monitoring signals

6. 6 CALO meeting 22.04.04 Anatoli Konoplyannikov Description Transmission Line Length (m)Delay (ns) PS/SPDECALHCALPS/SPDECALHCAL 1FE crate back planeparallel bus0.3 222 2 LED triggering signal distribution cables Twisted pair2514 12570 3 LED light distribution to PMT optic fiber2.51.5 ?2.215.41415.4 4 PMT signal transmission cable coax cable2512161256080 Total Delay (ns) =267.4146167.4 Total Delay exclude PM signal cable142.48687.4 Total Coarse Delay (Clk cycles)644 Needed Coarse Delay (Clk cycles)911 5 LED light distribution to PIN diode optic fiber 0 6 PIN signal transmission cable coax cable 16 or 19 The data of the PS/SPD and ECAL cable length was taken from the Annecy report of 26.02.04. Table 2. An estimation of the propagation delay of the calorimeter sub-detectors LED monitoring signals and the calibration command coarse delay setting. Timing of the calorimeter monitoring signals

7. 7 CALO meeting 22.04.04 Anatoli Konoplyannikov Calibration signal time alignment with CLK. As was mentioned above, the calibration signal time-alignment with CLK is needed. In the same time for a LED triggering the calibration command must be transformed in to a pulse of 25 (50) ns width with variable delay up to 25 ns with step of order 1 ns. The DelayChip, developed at LAL, unfortunately is not a programmable delay line, but it is a phase clock shifter with an optimal frequency of about 40 MHz. For solving all these problem, the individual output shaper on LED trigger signal board is offered. The circuit and timing diagrams of the shaper is shown on figure. Timing of the calorimeter monitoring signals

8. 8 CALO meeting 22.04.04 Anatoli Konoplyannikov Timing of the calorimeter monitoring signals The circuit and timing diagrams of the output LED triggering shaper.

9. 9 LED triggering signal distribution board status (April 2004) CALO meeting 22.04.04 Anatoli Konoplyannikov Sins the last LHCb meeting I’ve got the few oral answers from the calorimeter sub-detector groups on the questions about needed quantity of the LED triggering signals and an estimation of the trigger signal distribution cable length. Thanks this feedback the specification of the LEDTSB board has been updated: 1.64 output channels of the LEDTSB board is divided on four group with an individual Coarse delay up to 15 clock cycles with a time step of 25 ns. 2.Each output channel is equipped with the shaper for synchronization with Clock and generation a pulse of the 25 (50) ns width.

10. 10 LED triggering signal distribution board status (April 2004) CALO meeting 22.04.04 Anatoli Konoplyannikov Updated block diagram of the LED trigger signal distribution board.

11. 11 CALO meeting 22.04.04 Anatoli Konoplyannikov LEDTSB boards,the same size as LFB board, will be placed in the FE crate, FPGA will be placed on a mezzanine card for simplifying the chip exchange from non radhard to radiation hard ACTEL chip, Number of channels – 64 (60) divided on four group with individual delay line that varies from 0 to 15 clock cycles with 25 ns step, 16 (15) and output connectors RJ45 type on a front panel, A level of the output signals is LVDS, A program adjustable delay is in the range 25 ns with a step 1 ns per each channel, A LED trigger signal width is 25 ns, Memory of the scanning algorithm FPGA with 64 patterns of the output trigger signals allows perform all needed sequences for LED flashing, SPECS slave mezzanine card (developed in LAL) is used for connection with ECS and TTCrx decoding, There are two operational mode: A) The main mode, when the LED trigger signals are generated from TTCrx command, B) The trigger signals are generated from internal generator (Freq. ~ 1 kHz). 9U VME 64 – channel LED Trigger Signal Board (LEDTSB) specification

12. 12 LED triggering signal distribution board status (April 2004) CALO meeting 22.04.04 Anatoli Konoplyannikov Conclusion The timing estimation of the LED monitoring signal has been done. The propagation delay of the monitoring signals are different for the CALO sub- detectors and varies from 4 to 6 clock cycles. Therefore the coarse delay of the LEDTSB board in the sub-detector crates must be set taking into account this difference and total delay must be 16 clock cycles. The calibration signal time alignment with CLK is needed too and will be implemented in the LEDTSB board. The LED triggering signal board specification has been updated. Now the four signal group has an additional up to 375 ns common coarse delay and each signal into the group has an individual 25 ns delay with 1 ns step.